Nitride semiconductors are used in various semiconductor devices such as semiconductor light emitting devices and HEMT (high electron mobility transistor) devices. However, the characteristics of such nitride semiconductor devices are restricted by high density threading dislocations due to lattice mismatch with the GaN crystal.
Semiconductor light emitting devices or LED (light emitting diode) devices based on nitride semiconductors are expected as a phosphor-exciting light source for e.g. white LED. However, the problem is that high light emission efficiency, or high optical output, cannot be achieved when the output power is increased.
Various proposals have been made to increase the efficiency of LED and other semiconductor light emitting devices based on nitride semiconductors.